Omnidirectional aerials



May 5, 1959 JEAN-CLAUDE SIMON ET AL 2,

' OMNIDIRECTIONAL AERIALS Filed May 17, 1955 United States Patent OMNIDIRECTIONAL AERIALS Jean-Claude Simon and Georges Weill, Paris, France, assignors to Compagnie Generale de Telegraphie Sans Fil, a corporation of France Application May 17, 1955, Serial No. 509,011 Claims priority, application France May 28, 1954 7 Claims. (Cl. 343-755) The invention relates to short or ultra-short electromagnetic wave aerials having a substantially omnidirectional radiation diagram and a horizontally polarized electric field.

Aerials are known which have a radiating element consisting of a series of discs or other parallel metallic elements arranged along an axis. The whole constitutes a medium known as an artificial dielectric propagating a plane wave radiated along the axis from one of the extremities of the aerial, the other extremity being excited by means of a wave-guide through a matching device. The gain of such aerials can be improved by varying either the diameter or the spacing of successive discs or both of these parameters, the curve plotting the variation of these parameters against the distance along the axis, such structure causing a variation, along the axis, of the refraction index of the propagation medium.

The object of the invention is to produce an aerial constituted by an artificial dielectric medium, but radiating in a plane perpendicular to the vertical aerial axis, the radiation diagram being substantially omni-directional in that plane, and the ultra-high frequency electric field being horizontally polarized.

The aerial according to the invention comprises a diffracting element consisting of a series of metal discs centered on a metal rod constituting the aerial axis and having a diameter comprised between A/2+K7\ and A-l-KA, K 'being any whole number and the wavelength in free space of the ultra-high frequency energy radiated, either or both of the spacing and diameter of successive discs being variable, the curve of variation of which plotted against the distance along the axis displaying at least one maximum and one minimum along the aerial axis, the diameters of the successive discs remaining within the above-defined limits and the respective spacings of the successive discs being of the order of the wavelength. The aerial further comprises an excitation device of known type and producing a circularly polarized field, and a device for matching the excitation device to the radiating element to avoid reflection of the waves by the latter, which would cause irregularities in the aerial radiation diagram, said device consisting of a series of parallel metal discs, centered on said metal rod, said discs having a diameter less than M2, A being the operating wavelength, and the distance between the successive discs being of the order of A/ 10.

The invention will be better understood by means of the following description with reference to the single figure of the accompanying drawing which is a perspective view of a non-restrictive example of an aerial arrangement in accordance with the invention.

In the example illustrated in the single figure, the diffracting or radiating element consists of five successive metal discs d d the diameters of which being comprised between 2 and A, said discs being arranged parallel to one another on a central metal rod T, the spacing of said discs being of the order of A. If 1 1 1 1 are respectively the distances between the discs al -d d,-d

ice

2 (1 -11 d -d said distances are chosen in the embodiment shown in the figure in such manner that The excitation system may comprise a coaxial line G with a bell-mouthed end K and a helix H. This arrangement supplies a wave with a circularly polarized electric field. This wave is transmitted to the transmission and matching system consisting of discs a a a;;. The diameter of the latter is less than 7t/ 2 and their respective spacing m m does not exceed M3. It is generally of the order of M5.

A metal disc R acts as a reflector. Rods S S S S S and S constitute a frame which supports the aerial.

The excitation system described above is known and could be replaced by any other known system producing a circularly polarized field. The transition and matching system avoids reflection of the waves emitted by excitation device, such reflection being liable to cause irregularities in the aerial radiation diagram.

It should be noted that the diameter of discs a a a is less than 2, whereas that of discs d d is comprised between \/2 and 7t. Theory actually shows and experiment confirms that a succession of discs satisfying the first condition d \/2, d being the diameter of a disc produces propagation of'the wave along the axis without lateral radiation, whereas a succession of discs satisfying the second condition (A/2 d produces lateral radiation of the wave, this efiect being actually that required for the diifracting element.

The length of the whole aerial is between about SA and 10x.

An aerial has been constructed with the following data:

, \=9.3 cm. in free space (1) radiating device:

diameters of the discs d d d d d substantially equal to 3 M4 (2) matching device: m =m =O.2 diameter of the discs a a (1 substantially equal to M4 (3) excitation device: Length of the helix H=1.87)\

length of the whole aerial= 6.787\

This aerial has given the following performance:

Gain: of the order of 9 db Radiation diagram: Omnidirectional to within 1 db.

What we claim is:

1. An aerial for radiating a plane-polarized ultra-high frequency wave omnidirectionally in a given plane of polarization comprising, a metallic rod having its axis extending perpendicular to said plane, a plurality of metal discs mounted coaxially on said rod and having respective diameters ranging from about A/Z-l-KX to )\+K)\, wherein A is the Wave length in free space of the wave to be radiated and K is an integer, the axial spacing between adjacent discs being comprised between M2 and 3M2, said axial spacing and said diameters being geometrical parameters at least one of the geometrical diameter and spacing parameters of said discs varying lengthwise of said rod to produce a curve different from a straight line parallel to the abscissae for the variation thereof plotted against the distance along said axis, means for exciting a circularly polarized ultra-high frequency field having its axis of polarization coincident with said axis, and matching means as between said exciting means and loaded rod substantially to prevent reflections.

2. An aerial for radiating a plane-polarized ultra-high distance along said axis, means for exciting a circularly polarized field having its axis of polarization coincident with said axis, and matching means as between said exciting means and loaded rod substantially to prevent reflections.

3. An omnidirectional aerial for transmitting an horizontally polarized electric ultra-high frequency wave, comprising in combination: a metallic rod having a vertical axis; diffracting and radiating means comprising a first succession of metallic discs centered on said rod, and having respective diameters comprised between A/2+K7\, and \+K A being the wavelength in free space of the wave to be emitted, K being an integer, the respec' tive distance between said discs being comprised between 2 and 3M2; an excitation device for producing an ultrahigh frequency field circularly polarized around said axis; and means for matching said device to said radiating means comprising a second succession of discs centered on said rod, and located between said first succession of discs and said device, said discs having a diameter smaller than M2, and the respective distance therebetween being of the order of M 10.

4. An omnidirectional aerial for transmitting an horizontally polarized electric ultra-high frequency wave, comprising in combination: a metallic rod having a vertical axis; diffracting and radiating means comprising a first succession of metallic discs centered on saidrod, which are non uniformly spaced and having respective diameters comprised between A/Z-i-KA, and )l-i-KA, A being the wavelength in free space of the wave to be transmitted, K being an integer, the respective distance between said discs being comprised between )\/2 and 3 2; the distance between said successive discs being variable, an excitation device for producing an ultra-high frequency field circularly polarized around said axis; and means for matching said device to said radiating means comprising a second succession of discs centered on said rod, and located be- 4 tween said first succession of discs and said device, said discs having a daimeter smaller than M2, and the repective distance therebetween being of the order of M10.

5. An aerial according to claim 2, wherein said excitation device comprises a metallic helix wound around said axis.

6. An aerial for radiating a plane-polarized ultra-high frequency w-ave'omnidirectionally in a given plane of polarization, comprising a metallic rod having its axis extending perpendicular to said plane, a plurality of metal discs mounted coaxially on said rod, the axial spacing between said discs varying lengthwise of said rod, means for exciting a circularly polarized field having its axis of polarization coincident with said axis, and matching means as between said exciting means and loaded rod substantially to prevent reflections.

7. An omnidirectional aerial for transmitting an horizontally polarized electric ultra-high frequency wave, comprising in combination: a metallic rod having a vertical axis; difiracting and radiating means comprising a first succession of metallic discs centered on said rod, and having respective diameters comprised between A/Z-l-KA, and \+K Nbeing the wavelength in free space of the Wave to be transmitted, K being an integer, the respective distance between said discs being comprised between M2 and 3M2, the diameter of said discs being variable, an excitation device for producing an ultra-high frequency field circularly polarized around said -axis;'and means for matching said device to said radiating means, comprising a second succession of discs centered on said rod, and locatedbetweensaid first succession of discs and said device, said discs having a diameter smaller than M2, and the respective distance therebetween being of the order of A/ 10.

References Cited in the file of this patent UNITED STATES PATENTS 2,503,010 Tiley Apr. 4, 1950 2,588,610 Boothroyd et al. Mar. 11, 1952 2,663,797 Kock' Dec. 22, 1953 FOREIGN PATENTS 1,058,284 France Nov. 4, 1953 

